Abstract : Photonic crystal cavity-based switching is studied both theoretically and experimentally in order to identify the best conﬁguration to maximize -wavelength conversion- eﬃciency. In particular, it is shown that an enhanced contrast can be reached when the probe is blue-shifted with respect to the resonance. The use of an InP-SOI hybrid photonic crystal nanocavity is reported for the ﬁrst time for all-optical error-free -wavelength conversion- at 20 Gbit-s with an NRZ-OOK signal.